KVM: x86/mmu: Don't freak out if pml5_root is NULL on 4-level host
Include pml5_root in the set of special roots if and only if the host, and thus NPT, is using 5-level paging. mmu_alloc_special_roots() expects special roots to be allocated as a bundle, i.e. they're either all valid or all NULL. But for pml5_root, that expectation only holds true if the host uses 5-level paging, which causes KVM to WARN about pml5_root being NULL when the other special roots are valid. The silver lining of 4-level vs. 5-level NPT being tied to the host kernel's paging level is that KVM's shadow root level is constant; unlike VMX's EPT, KVM can't choose 4-level NPT based on guest.MAXPHYADDR. That means KVM can still expect pml5_root to be bundled with the other special roots, it just needs to be conditioned on the shadow root level. Fixes: cb0f722a ("KVM: x86/mmu: Support shadowing NPT when 5-level paging is enabled in host") Reported-by:Maxim Levitsky <mlevitsk@redhat.com> Reviewed-by:
Maxim Levitsky <mlevitsk@redhat.com> Signed-off-by:
Sean Christopherson <seanjc@google.com> Message-Id: <20210824005824.205536-1-seanjc@google.com> Signed-off-by:
Paolo Bonzini <pbonzini@redhat.com>
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